1. Field of the Invention
The invention relates generally to non-invasive methods and systems for probing the earth, and more specifically to radio instruments that can image and detect objects and other anomalies in the ground. Leakage pathways in levee and earth dams is an example of an anomaly that cannot be seen by surface observation.
2. Description of the Prior Art
Underground facilities cannot totally disappear from the surface the way modern submarines can beneath the sea. Many reasons exist for finding underground facilities, e.g., law enforcement needs to be able to detect and assess illegal tunnels bored under international borders by drug smugglers. There is generally a lack of primary access to such underground facilities, so methods need to be developed that can collect and recognize the telltale signs.
For many reasons, the worldwide mining industry has developed a standard practice that results in electrical conductors being installed in the adit and passageways of underground industrial developments and facilities. Recent work in developing mine-wide radio system equipment has shown that the electrical conductors form a low attenuation rate network, or waveguide, for electromagnet (EM) wave distribution into and throughout the complex. Leakage pathways through clay bearing soil also form electrical conductors. Deliberate or fortuitous EM-wave generators can induce currents in such conductors. Deliberate EM-wave generators can be deployed to the survey site, while fortuitous ones already illuminate the site with spurious signals.
Much of the relevant background art is documented in the many United States Patents of the present inventor, Larry G. Stolarzyck. Such Patents are listed in Table I, and are incorporated herein by reference.
Briefly, a method embodiment of the present invention finds underground mines, tunnels, shafts and leakage pathways from above ground electronic measurements by assuming they will be built or occur in a particular way and decorated with a variety of standard features. Concrete reinforcing bar, rails, pipes, and wire cables are assumed to coexist. When illuminated by radio waves that penetrate the ground, these conductive metals will reradiate secondary electromagnetic signals that can be observed on the surface. Radio signal measurements collected above ground are combined into pictures and estimates of the scope, orientation, nature, and character of the underground structures. Changes over days, weeks, months, and years can be interpreted as being the result of deterioration, damage, upgrades, expansion, new construction, design changes, etc.
An advantage of the present invention is that a method for imaging underground facilities is provided that can use opportunistic sources of radio illumination.
Another advantage of the present invention is that a system for imaging an underground facility can be dropped in and results can be read in real-time.
A further advantage of the present invention is that a system for imaging an underground facility can be mounted in a car, operated passively, and the results can be read in real-time.
These and other objects and advantages of the present invention will no doubt become obvious to those of ordinary skill in the art after having read the following detailed description of the preferred embodiment which is illustrated in the various drawing figures.